1. Field of the Invention
The present invention pertains to a subterranean electrode well having improved electrodes formed by generally horizontally extending flexible metallic tubes which extend radially outward from the wellbore and are in electrically conductive communication with a conductor extending within the well from a surface source of electrical energy.
2. Background
In the continuing effort to develop subterranean formations which contain large deposits of viscous hydrocarbons, there have been several proposals to reduce the viscosity and improve the flowability of the hydrocarbon materials by passing electric current through the formation to achieve resistance heating of the formation and to thereby lower the viscosity of the hydrocarbon materials contained therein.
One of the problems with developing resistance heating of subterranean formations pertains to the rather localized heating which occurs at the interface between the electrode structure and the formation itself. This localized heating can be so intense as to vaporize the fluids in the vicinity of the electrode thereby reducing electrode contact with the formation and the distribution of the resistance heating through the formation itself.
One proposal for increasing the electrode contact area with the formation structure is disclosed and claimed in U.S. Pat. No. 4,084,639 to J. C. Todd and assigned to the assignee of the present invention. This patent discloses an arrangement of an electrode well which includes a plurality of electrically conductive rods which extend radially outwardly from a central wellbore to provide increased electrode area for conducting current into the subterranean formation. However, the radial extent of the rod members described in the Todd reference is limited by the configuration of the apparatus itself and the rods penetrate the formation only to the extent that mechanical displacement will permit.
It has also been proposed in the art of developing subterranean reservoirs containing hydrocarbon substances to drill horizontal boreholes radially outward from a vertical wellbore by extending a bendable metal tube, sometimes referred to as coiled tubing, into the formation by hydraulically jetting or eroding the formation in the path of the tube to form the horizontal borehole. The tubing is extended radially outward from the borehole axis using a whipstock apparatus which is constructed to enable the tubing "drill string" to move from the vertical borehole through a relatively short radius ninety degree turn. This method of drilling horizontal boreholes is completed by electrochemical milling of the radially extended tube in the vicinity of its departure from the wellbore to, in effect, disconnect the tube from the well casing or structure upon completion of the horizontal borehole itself.
Other techniques have been developed for drilling so-called horizontal drain holes which extend generally radially outward from a conventional vertical wellbore to enhance the recovery of hydrocarbon substances of subterranean formations. These drain hole drilling processes typically involve the rotation of a drill stem having an articulated or flexible section and to which is connected a conventional rotary bit. Alternatively, some drain hole drilling processes contemplate the utilization of a downhole fluid operated drilling motor which must be retrieved after completion of the drilling process.
It is an object of the present invention to provide an improved electrode well for enhanced hydrocarbon recovery operations from subterranean formations wherein the electrode contact area is significantly increased as compared with conventional electrode wells. It is another object of the present invention to provide an electrode well wherein a plurality of current conducting and fluid conducting conduits are extended radially outwardly in selected directions from a substantially vertical wellbore and are electrically connected to conductor means in the wellbore. The tubes are also maintained in fluid flow communication with the wellbore for conducting an electrolyte into the formation or, alternatively, producing fluids from the formation through the wellbore. These objects and other features of the present invention are described in further detail herein.